In this work complete analytical modeling, simulation with experimental verification of photovoltaic system driving reverse osmosis water desalination is presented. In photovoltaic system, solar radiation and PV generation modeling is done and investigation of the effect of fixed and tracking PV panel on the collected insolation and PV power is carried out. In the RO section, complete model of RO membrane is developed that estimates the feed water pressure and permeate flow rate. The developed PV and RO models are validated individually as well as integrated (combined PVRO) by experimental data and show good agreement. By using this validated model the effect of slope and azimuth angle of the PV panel is studied on the permeate flow rate for the whole year. The increments in the clean water flow rate for the yearly tilt, monthly tilt, single and double axis tracking PV panels with respect to traditional flat panel is computed. The estimated results reveal that yearly optimal tilt angle of PV panels due south is close to the 0.913 times latitude of the Dhahran city. Yearly permeate gain with the yearly optimal tilt, monthly optimal tilt of PV panel relative to flat panel installation is 10% and 19% respectively. The optimization of photovoltaic system suggests the adjustment of the PV orientation (tilt angle and azimuth angle) by using a single and dual axis tracking system installations. The yearly permeate gain made by single and double axis continuous tracking PV panels is 43% and 62% respectively. (C) 2014 Elsevier Ltd. All rights reserved.